Hands-down, and big thanks to @aeschli for his amazing contribution to onigasm's internal mechanisms.
2.2.0 is now 3x faster than previous version, with benchmarks run against samples containing huge number of multibyte characters*. Worst case scenario that is.
Further improvements coming soon! Until then, please run npm i onigasm again to get the update.
* Characters ranging from codepoint 100 to 500